metering for a dodge 318

[74 Powerwagon]

Hi, I have rebuilt a quadrajet for my dodge 318 and would like some input from members on proper primary and secondary metering. I have a 74 W100 with only 90k miles, it's a retired park service truck. I will be putting on a 340 spreadbore intake and a rv cam with .429/.444 lift and 209/220 duration. The carb #17081206 is from a 81 Chevy pickup. I ordered some primary rods and jets from Cliff, not sure what size as I just ordered them. I have 3 different secondary rods that could work, I have DR, DP, & CH rods. I also have hangers H, L,M,N,P,R, & S to choose from. I have Cliff's book which is a great help with upgrades. I want to get the carb set up right so I can Install it with the cam and new timing chain all at once to break in the cam. I also live at 9K in the rockies. Thanks for helping me out if you could, Kent.

[Ethan1]

Hi, I have rebuilt a quadrajet for my dodge 318 and would like some input from members on proper primary and secondary metering. I have a 74 W100 with only 90k miles, it's a retired park service truck. I will be putting on a 340 spreadbore intake and a rv cam with .429/.444 lift and 209/220 duration. The carb #17081206 is from a 81 Chevy pickup. I ordered some primary rods and jets from Cliff, not sure what size as I just ordered them. I have 3 different secondary rods that could work, I have DR, DP, & CH rods. I also have hangers H, L,M,N,P,R, & S to choose from. I have Cliff's book which is a great help with upgrades. I want to get the carb set up right so I can Install it with the cam and new timing chain all at once to break in the cam. I also live at 9K in the rockies. Thanks for helping me out if you could, Kent.

 Kent,
 Welcome to CHP!

 Is your carb a SMAB (single main air bleed) carb? Or dual?

 If SMAB, I would use a 52M Primary Metering Rod. If dual, .044" tip Primary Metering Rod, Cliff, has.

 Those secondary rods I think are a little too big. But, I don't know how much +.002" variance makes difference wise. So, I will leave that to the experts.

 All your hanger's will work except for the "H". I would go with the "L".

[Ethan1]

 Do you have any CV or AU  secondary rods?

[74 Powerwagon]

  Thanks Ethan. The carb is a SMAB that is .082 in size. I ordered a set of primary rods and jets from Cliff so that will be well paired. I can get a a pair of CK secondary rods which are the same as AU rods. I also already have some DA rods, but they are probably too rich for the 318. Thanks for your help! I'll post when I get everything on the engine. I'm doing some light porting to a pair of stock heads and then getting fresh guides and 3 angle valve job with new valves. Kent

[74 Powerwagon]

I just ordered a set of CK secondary rods, they are the same as the AU rods. Thanks for your time and expertise Ethan, Kent

[Ethan1]

I just ordered a set of CK secondary rods, they are the same as the AU rods. Thanks for your time and expertise Ethan, Kent

 Yes they are, Kent. You're welcome bud! Ethan

[74 Powerwagon]

I recently rebuilt this carb with a kit from Cliff and added a fuel pressure regulator as the carb started flooding gas out of the vent. It runs good now, I also adjusted the APT to fix an off idle stumble. My issue is that I can adjust the idle mix screws all the way in and the engine doesn't die, that includes both screws all the way closed. I can see if loosening the idle speed screw with mix screws closed will kill it. I live at 9k in the Rockies and am wondering if I may need some more idle bypass air to make up for the thin air. It does idle down with the speed adjustment. The bypass air holes are currently .055. Thanks to all for the advice.

[Cliff Ruggles]

How big are the holes under the mixture screws?

Does the engine slow down when you turn the mixture screws in?

It's common not to be able to kill off the engine as there is still some transfer slot exposed at idle to give it fuel, but you should have control with the mixture screws by being able to lean it up enough to slow it down some.

Also curious why it would be flooding out the vent with new parts installed.  Those carbs can handle a lot of fuel pressure without issue........Cliff

[74 Powerwagon]

Hi I noticed that I goofed when I assembled the needle and seat and the needle fell off the float, once I put it back on the float and checked by blowing in the inlet with the carb upside down the needle and seat worked fine. The flooding issue was why I got the kit and a regulator to make sure my fuel pressure wasn't too high. It is now at 5psi steady and doesn't leak.
I drilled the mixture screw ports out to.093 and shortened the springs. The engine did not slow much if any with the idle mix screws, the idle speed adjustment does slow idle speed. The original idle bypass air is .055 and I haven't enlarged it.
Should I loosen the idle speed adjustment so it isn't on the butterfly shaft at all, or only just touching, and then see if the idle mix screws have any effect? Maybe the springs on the idle mix screws are still too long and the screws aren't closed when they bottom out the springs.
Thank you Cliff for sharing your extensive experience with us.

[Cliff Ruggles]

You mentioned changing the camshaft and timing set.  What cam did you install in the engine?

What is the compression ratio?

What timing set?

[74 Powerwagon]

I haven't changed that yet. Work complications and now job searching has not allowed for that. Engine is stock 74 318 with a mopar 340 spreadbore intake.

[Cliff Ruggles]

First step would be to install the mixture screws without springs on them, so they can actually bottom out and see if you have control enough to at least lean it up and slow the engine down some.  It still might not stall it out, as some fuel is available from the exposed portion of the transfer slots at idle.......Cliff